The methodology of choosing a user group is also important. Because of the very
wide diversity of the sensory, motor, and cognitive characteristics of older people, as
well as in their education and technical background, one is never likely to obtain a
“representative sample” of the user group as can happen when the user group is much
more constrained. Thus the users to be tested must be picked with care to illustrate
those characteristics which the researchers believe important. It is thus important that
an adequate cohort of older people is available to the experimenter, and it is valuable
to form a long-lasting partnership with them [7